As the parenteral drugs become more and more popular, medication injection devices are expected to be widely used. Pre-filled syringe and patient self-use autoinjector are the current forms of medication injection devices used for delivering parenteral drugs. Examples of pre-filled syringe can be found in U.S. Pat. Nos. 6,189,292 and 7,428,807. Examples of autoinjector device can be found in U.S. Pat. Nos. 7,794,432 and 8,808,250. Using pre-filled syringe and autoinjector device can ease medication preparation/administration procedure and reduce needle injury, which results in improved patient convenience and compliance. There are a number of mechanical autoinjector devices designed for patient self-injection. However, there is no mechanical assisting medication delivery device designed for health care professionals who deliver medication to patients. This gap lead to following issues for health care professionals—    a. Without mechanical assisting mechanism, manual pre-filled syringe is not ergonomic for multiple injections in a repetitive manner, which is often the case for healthcare professionals.    b. For medication formulation with high viscosity and high delivery volume, it requires extra finger force for successful delivery using the manual pre-filled syringe. This is not optimal for healthcare professionals.    c. The current mechanical autoinjector devices are designed based on the human factor needs for patient self-injection. Therefore, the designs are often inconvenient for healthcare professional to use, from the human factor point of view.
Furthermore, the sizes of current mechanical autoinjector devices are large, which is unnecessary for most hospital setting and waste materials for single injection. Therefore, injection devices based on a novel design principal are in need.